Start on Android fast app resume.

Ref: http://forums.xamarin.com/discussion/621/androidgameview-pause-without-losing-gl-context/p2
Move DeviceResetting to when the Context is lost, which is where it should be now. Fast app resume works!

Fixes #2600
Add a listener for ScreenSize changes too so we get killed less often, requires building with SDK 3.2+ (4.0+ with Xamarin)

ref http://forums.xamarin.com/discussion/comment/60864/#Comment_60864
Merge remote-tracking branch 'origin/develop' into android-fast-app-resume
Merge pull request #2753 from danzel/android-fast-app-resume

Android fast app resume